This invention relates to fuel metering systems for controlling the mass ratio of fuel and air supplied to an internal combustion engine and seeks generally to provide improvements in such systems of the general character shown in U.S. Pat. No. 3,817,225 and U.S. Pat. application Ser. No. 428,261 filed Dec. 26, 1973, now U.S. Pat. No. 3,935,851.
In such prior forms of fuel metering system or apparatus, the metering and programming functions are so combined and implemented that the mass flow corrections to the fuel and air signals for ambient fluid density parameter variations are accurate for only one value or limited range of variation of the desired fuel-air ratio schedule or the latter may be accurate for only one set or a limited range of variation of the ambient fluid conditions, so that the systems do not satisfy the desired fuel-air metering relation over the entire range of engine operation and ambient conditions.
The present invention seeks to provide a fuel metering system in which the fuel metering and programming functions are distinct and are implemented in a manner such that the actual mass fuel-air ratio is accurately and precisely controlled and maintained in accordance with a predetermined desired fuel metering relation over the entire range of engine operation and ambient fluid parameter variations.
Related objects are to provide a fuel metering system which is designed and operated in such a manner as to provide greater accuracy, precision and flexibility over known prior systems while affording simplification and reduction in the cost of implementation thereof.
Other objects are to provide a fuel metering system which is suitable for mass production, large scale use on automotive vehicle engines and improves the performance, fuel consumption and emissions levels of internal combustion engines in such vehicles.